Ciro Santilli @cirosantilli 37

A polynomial of degree 1, i.e. of form $ax+b$.

As of 2020, no one knows how to build the major desktop distros fully from source into the ISO, and especially so in a reproducible build way. Everything is done in build servers somewhere with complicated layers of prebuilds. It's crap.

See also: cirosantilli.com/linux-kernel-module-cheat/#linux-distro-choice

Yes:

No:

The first quantum mechanics theories developed.

Their most popular formulation has been the Schrödinger equation.

A computer model that is as powerful as the most powerful computer model we have: Turing machine!

Turing machine regex tape notation is Ciro Santilli's made up name for the notation used e.g. at:Most of it is just regular regular expression notation, with a few differences:

This notation is very useful, as it helps compress long repeated sequences of Turing machine tape and extract higher level patterns from them, which is how you go about understanding a Turing machine in order to apply Turing machine acceleration.

What if Process 1 tries to access 0x00003000, which is not present?

The hardware notifies the software via a Page Fault Exception.

When an exception happens, the CPU jumps to an address that the OS had previously registered as the fault handler. This is usually done at boot time by the OS.

This could happen for example due to a programming error:but there are cases where it is not a bug, for example in Linux when:

In any case, the OS needs to know which address generated the Page Fault to be able to deal with the problem. This is why the nice IA32 developers set the value of cr2 to that address whenever a Page Fault occurs. The exception handler can then just look into cr2 to get the address.

Why are pages 4 KiB anyways?

There is a trade-off between memory wasted in:

This can be seen with the extreme cases:

x86 designers have found that 4 KiB pages are a good middle ground.

All with olive oil and salt mixed up before roasting.

2021-04-05 180C:

2021-02-06 180C:

2021-01-04:

2020-11-21:

Physical address extension.

With 32 bits, only 4GB RAM can be addressed.

This started becoming a limitation for large servers, so Intel introduced the PAE mechanism to Pentium Pro.

To relieve the problem, Intel added 4 new address lines, so that 64GB could be addressed.

Page table structure is also altered if PAE is on. The exact way in which it is altered depends on weather PSE is on or off.

PAE is turned on and off via the PAE bit of cr4.

Even if the total addressable memory is 64GB, individual process are still only able to use up to 4GB. The OS can however put different processes on different 4GB chunks.

www.urbandictionary.com/define.php?term=turd%20polishing on Urban Dictionary.

Ciro Santilli learned this expression from Angry Video Game Nerd.

The key question is: why is this not symmetrical?

One answer is: because one of the twin accelerates, and therefore changes inertial frames.

But the better answer is: understand what happens when the stationary twin sends light signals at constant time intervals to each other. When does the travelling twin receives them?

By doing that, we see that "all the extra aging happens immediately when the twin turns around":

Another way of understanding it is: you have to make all calculations on a single inertial frame for the entire trip.

Supposing the sibling quickly accelerates out (or magically starts moving at constant speed), travels at constant speed, and quickly accelerates back, and travels at constant speed setup, there are three frames that seem reasonable:

If you do that, all three calculations give the exact same result, which is reassuring.

Another way to understand it is to do explicit integrations of the acceleration: physics.stackexchange.com/questions/242043/what-is-the-proper-way-to-explain-the-twin-paradox/242044#242044 This is the least insightful however :-)

Bibliography:

Hardcoded and unique network addresses for every single device on Earth.

Started with 48 bits (6 bytes), usually given as 01:23:45:67:89:AB but people now encouraged to use 64-bit ones.

How they are assigned: www.quora.com/How-are-MAC-addresses-assigned Basically IEEE gives out the 3 first bytes to device manufacturers that register, this is called the organizationally unique identifier, and then each manufacturer keeps their own devices unique.